A sensor network may include distributed autonomous sensors. Uses of sensor networks include but are not limited to military applications, industrial process monitoring and control, machine health monitoring, environment and habitat monitoring, utility usage, healthcare applications, home automation, and traffic control. A node in a sensor network is typically equipped with one or more sensors, a communications interface, a controller, and an energy source (such as a battery). Sensor nodes may vary considerably in size, and their cost may be similarly variable. Size and cost constraints on sensor nodes result in corresponding constraints on resources such as energy, memory, computational speed and bandwidth.